SOLUTION: Please help me find the sum of the following series: t1 = -4 tn = 66 n = 15

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Question 1162979: Please help me find the sum of the following series:
t1 = -4
tn = 66
n = 15
Answer by ikleyn(52788) About Me  (Show Source):
You can put this solution on YOUR website!
.

Find the average of the first and last terms  A = %28t1+%2B+tn%29%2F2 = %28-4+%2B+66%29%2F2 = 62%2F2 = 31.


Then multiply it by the number of term.  You will get the value of the sum = 31*15 = 465.  ANSWER

Solved.

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For introductory lessons on arithmetic progressions see
    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions
in this site.

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The referred lessons are the part of this online textbook under the topic "Arithmetic progressions".


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Free of charge online textbook in ALGEBRA-II
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